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D.C. Generators

Study 120 Electrical Engineering MCQs with correct answers and explanations.

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61Electrical EngineeringMedium

The terminal voltage of a D.C. shunt generator drops on load because of all of the following reasons except:________?

Afield weakening due to armature reaction and armature

Bcommutation

Carmature reaction

Darmature resistance drop

Correct answer

B. commutation

Explanation

The correct answer is commutation.

62Electrical EngineeringMedium

In D.C. generators, the brushes on commutator remain in contact with conductors which________?

Alie under south pole

Bare farthest from the poles

Clie under north pole

Dlie under interpolar region

Correct answer

D. lie under interpolar region

Explanation

The correct answer is lie under interpolar region.

63Electrical EngineeringMedium

In a D.C. generator in order to reduce sparking at brushes, the self-induced e.m.f. in the coil is neutralised by all of the following except________?

Adummy coils

Bcompensating winding

Cshifting of axis of brushes

Dinterpoles

Correct answer

A. dummy coils

Explanation

The correct answer is dummy coils.

64Electrical EngineeringMedium

In a D.C. generator the number of mechanical degrees and electrical degrees will be the same when________?

Ar.p.m. is less than 300

Bnumber of poles is 4

Cnumber of poles is 2

Dr.p.m. is more than 300

Correct answer

C. number of poles is 2

Explanation

The correct answer is number of poles is 2.

65Electrical EngineeringMedium

The demagnetising component of armature reaction in a D.C. generator________?

Aincreases armature speed

Breduces generator e.m.f.

Creduces interpoles flux density

Dresults in sparking trouble

Correct answer

B. reduces generator e.m.f.

Explanation

The correct answer is reduces generator e.m.f..

66Electrical EngineeringMedium

In a level compounded D.C. generator, full load terminal voltage is________?

Amore than no-load terminal voltage

Bless than no-load terminal voltage

Cnegligibly low

Dequal to no-load terminal voltage

Correct answer

D. equal to no-load terminal voltage

Explanation

The correct answer is equal to no-load terminal voltage.

67Electrical EngineeringMedium

For both lap and wave windings, there are as many commutator bars as the number of________?

Aslots

Bpoles

Carmature conductors

Dwinding elements

Correct answer

D. winding elements

Explanation

The correct answer is winding elements.

68Electrical EngineeringMedium

A D.C. welding generator has________?

Alap winding

Bduplex winding

Cany of the above

Dwave moving

Correct answer

A. lap winding

Explanation

The correct answer is lap winding.

69Electrical EngineeringMedium

The bearings used to support the rotor shafts are generally________?

Aneedle bearings

Bmagnetic bearmgs

Cball bearings

Dbush bearings

Correct answer

C. ball bearings

Explanation

The correct answer is ball bearings.

70Electrical EngineeringMedium

Flashing the field of D.C. generator means:________?

Acreating residual magnetism by a D.C. source

Bneutralising residual magnetism

Cmaking the magnetic losses of forces parallel

Dincreasing flux density by adding extra turns of windings on poles

Correct answer

A. creating residual magnetism by a D.C. source

Explanation

The correct answer is creating residual magnetism by a D.C. source.

Flashing the field of D.C. generator means:________?

Acreating residual magnetism by a D.C. source

Bneutralising residual magnetism

Cmaking the magnetic losses of forces parallel

Dincreasing flux density by adding extra turns of windings on poles

Correct answer

A. creating residual magnetism by a D.C. source

Explanation

The correct answer is creating residual magnetism by a D.C. source.